[libc] Implement fopen, fclose, and fread on the GPU

[jhuber6]

Summary

This patch implements the fopen, fclose, and fread functions on
the GPU. These are pretty much re-implemented from what existed but
using the new interface. Having this subset allows us to test the
interface a bit more strenuously since we can write and read to a file.

[JonChesterfield]

Linux has in-memory files that would be a good fit for testing this. Memfd. Gives you a block of allocated memory that acts like a file.

[jhuber6]

In D157622#4577353, @JonChesterfield wrote:

Linux has in-memory files that would be a good fit for testing this. Memfd. Gives you a block of allocated memory that acts like a file.

That's neat, would save us the temporary file. But I think it's a little out of scope since the test already exists and this patch just uses it.

libc/src/stdio/gpu/fopen.cpp

25

I should probably make this max out at the buffer size in case someone does fopen("foo.txt", /*ReallyLongString=*/str).

[jhuber6]

ping

[sivachandra]

OK for non-GPU parts.

libc/config/gpu/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdlib.realloc
     libc.src.stdlib.free
 
     # errno.h entrypoints
     libc.src.errno.errno
 
     # stdio.h entrypoints
     libc.src.stdio.puts
+    libc.src.stdio.fopen
+    libc.src.stdio.fclose
+    libc.src.stdio.fread
     libc.src.stdio.fputs
     libc.src.stdio.stdin
     libc.src.stdio.stdout
     libc.src.stdio.stderr
 
     # inttypes.h entrypoints
     libc.src.inttypes.imaxabs
     libc.src.inttypes.imaxdiv

libc/docs/gpu/support.rst

 stdio.h
 --------
 
 =============  =========  ============
 Function Name  Available  RPC Required
 =============  =========  ============
 puts           |check|    |check|
 fputs          |check|    |check|
-fclose                    |check|
-fopen                     |check|
+fclose         |check|    |check|
+fopen          |check|    |check|
+fread          |check|    |check|
 =============  =========  ============

libc/src/stdio/CMakeLists.txt

add_entrypoint_object(
       ${name}
       ALIAS
       DEPENDS
         .generic.${name}
     )
   endif()
 endfunction(add_stdio_entrypoint_object)
 
-add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/generic)
 if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
   add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+elseif(NOT LIBC_TARGET_ARCHITECTURE_IS_GPU)
+  add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/generic)
 endif()
 
+
 add_subdirectory(printf_core)
 add_subdirectory(scanf_core)
 
 add_entrypoint_object(
-  fopen
-  SRCS
-    fopen.cpp
-  HDRS
-    fopen.h
-  DEPENDS
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  fclose
-  SRCS
-    fclose.cpp
-  HDRS
-    fclose.h
-  DEPENDS
-    libc.include.stdio
-    libc.src.errno.errno
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
   clearerr
   SRCS
     clearerr.cpp
   HDRS
     clearerr.h
   DEPENDS
     libc.include.stdio
     libc.src.__support.File.file
HDRS
     funlockfile.h
   DEPENDS
     libc.include.stdio
     libc.src.__support.File.file
     libc.src.__support.File.platform_file
 )
 
 add_entrypoint_object(
-  fread_unlocked
-  SRCS
-    fread_unlocked.cpp
-  HDRS
-    fread_unlocked.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
-  fread
-  SRCS
-    fread.cpp
-  HDRS
-    fread.h
-  DEPENDS
-    libc.src.errno.errno
-    libc.include.stdio
-    libc.src.__support.File.file
-    libc.src.__support.File.platform_file
-)
-
-add_entrypoint_object(
   fwrite_unlocked
   SRCS
     fwrite_unlocked.cpp
   HDRS
     fwrite_unlocked.h
   DEPENDS
     libc.src.errno.errno
     libc.include.stdio

 add_entrypoint_object(
   remove
   ALIAS
   DEPENDS
     .${LIBC_TARGET_OS}.remove
 )
 
 # These entrypoints have multiple potential implementations.
+add_stdio_entrypoint_object(fopen)
+add_stdio_entrypoint_object(fclose)
+add_stdio_entrypoint_object(fread_unlocked)
+add_stdio_entrypoint_object(fread)
 add_stdio_entrypoint_object(puts)
 add_stdio_entrypoint_object(fputs)
 add_stdio_entrypoint_object(stdin)
 add_stdio_entrypoint_object(stdout)
 add_stdio_entrypoint_object(stderr)

libc/src/stdio/generic/CMakeLists.txt

-if(LIBC_TARGET_ARCHITECTURE_IS_GPU)
-  # The GPU build cannot use any generic implementations.
-  return()
-endif()
+add_entrypoint_object(
+  fopen
+  SRCS
+    fopen.cpp
+  HDRS
+    ../fopen.h
+  DEPENDS
+    libc.include.stdio
+    libc.src.__support.File.file
+    libc.src.__support.File.platform_file
+)
+
+add_entrypoint_object(
+  fclose
+  SRCS
+    fclose.cpp
+  HDRS
+    ../fclose.h
+  DEPENDS
+    libc.include.stdio
+    libc.src.errno.errno
+    libc.src.__support.File.file
+    libc.src.__support.File.platform_file
+)
+
+add_entrypoint_object(
+  fread_unlocked
+  SRCS
+    fread_unlocked.cpp
+  HDRS
+    ../fread_unlocked.h
+  DEPENDS
+    libc.src.errno.errno
+    libc.include.stdio
+    libc.src.__support.File.file
+    libc.src.__support.File.platform_file
+)
+
+add_entrypoint_object(
+  fread
+  SRCS
+    fread.cpp
+  HDRS
+    ../fread.h
+  DEPENDS
+    libc.src.errno.errno
+    libc.include.stdio
+    libc.src.__support.File.file
+    libc.src.__support.File.platform_file
+)
 
 add_entrypoint_object(
   fputs
   SRCS
     fputs.cpp
   HDRS
     ../fputs.h
   DEPENDS

libc/src/stdio/gpu/CMakeLists.txt

 add_header_library(
   gpu_file
   HDRS
     file.h
   DEPENDS
     libc.src.__support.common
-    libc.src.__support.CPP.string_view
-    libc.src.__support.RPC.rpc_client
+    .stdin
+    .stdout
+    .stderr
+)
+
+add_entrypoint_object(
+  fopen
+  SRCS
+    fopen.cpp
+  HDRS
+    ../fopen.h
+  DEPENDS
+    libc.include.stdio
+)
+
+add_entrypoint_object(
+  fclose
+  SRCS
+    fclose.cpp
+  HDRS
+    ../fclose.h
+  DEPENDS
+    libc.include.stdio
+)
+
+add_entrypoint_object(
+  fread
+  SRCS
+    fread.cpp
+  HDRS
+    ../fread.h
+  DEPENDS
+    libc.include.stdio
 )
 
 add_entrypoint_object(
   puts
   SRCS
     puts.cpp
   HDRS
     ../puts.h

libc/src/stdio/gpu/fclose.cpp

-//===-- Implementation of fclose ------------------------------------------===//
+//===-- GPU Implementation of fclose --------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "src/stdio/fclose.h"
-#include "src/__support/File/file.h"
+#include "src/stdio/gpu/file.h"
 
-#include "src/errno/libc_errno.h"
 #include <stdio.h>
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, fclose, (::FILE * stream)) {
-  int result = reinterpret_cast<__llvm_libc::File *>(stream)->close();
-  if (result != 0) {
-    libc_errno = result;
+  uint64_t ret = 0;
+  uintptr_t file = reinterpret_cast<uintptr_t>(stream);
+  rpc::Client::Port port = rpc::client.open<RPC_CLOSE_FILE>();
+  port.send_and_recv([=](rpc::Buffer *buffer) { buffer->data[0] = file; },
+                     [&](rpc::Buffer *buffer) { ret = buffer->data[0]; });
+  port.close();
+
+  if (ret != 0)
     return EOF;
-  }
-  return 0;
+  return static_cast<int>(ret);
 }
 
 } // namespace __llvm_libc

libc/src/stdio/gpu/file.h

port.send([=](rpc::Buffer *buffer) {
     buffer->data[1] = file;
   });
   port.recv_n(&buf, &recv_size, [&](uint64_t) { return buf; });
   port.recv([&](rpc::Buffer *buffer) { ret = buffer->data[0]; });
   port.close();
   return ret;
 }
 
+LIBC_INLINE uint64_t read(FILE *f, void *data, size_t size) {
+  if (f == stdin)
+    return read_from_stdin(data, size);
+  else
+    return read_from_stream(reinterpret_cast<uintptr_t>(f), data, size);
+}
+
 } // namespace file
 } // namespace __llvm_libc

libc/src/stdio/gpu/fopen.cpp

+//===-- GPU Implementation of fopen ---------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/fopen.h"
+#include "src/__support/CPP/string_view.h"
+#include "src/stdio/gpu/file.h"
+
+#include <stdio.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(::FILE *, fopen,
+                   (const char *__restrict path, const char *__restrict mode)) {
+  uintptr_t file;
+  rpc::Client::Port port = rpc::client.open<RPC_OPEN_FILE>();
+  port.send_n(path, internal::string_length(path) + 1);
+  port.send_and_recv(
+      [=](rpc::Buffer *buffer) {
+        inline_memcpy(buffer->data, mode, internal::string_length(mode) + 1);
+      },
+      [&](rpc::Buffer *buffer) { file = buffer->data[0]; });
+  port.close();
+
+  return reinterpret_cast<FILE *>(file);
+}
+
+} // namespace __llvm_libc

libc/src/stdio/gpu/fread.cpp

-//===-- Implementation of fread -------------------------------------------===//
+//===-- GPU Implementation of fread ---------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "src/stdio/fread.h"
-#include "src/__support/File/file.h"
+#include "src/stdio/gpu/file.h"
 
-#include "src/errno/libc_errno.h"
 #include <stdio.h>
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(size_t, fread,
                    (void *__restrict buffer, size_t size, size_t nmemb,
                     ::FILE *stream)) {
   if (size == 0 || nmemb == 0)
     return 0;
-  auto result =
-      reinterpret_cast<__llvm_libc::File *>(stream)->read(buffer, size * nmemb);
-  if (result.has_error())
-    libc_errno = result.error;
-  return result.value / size;
+  auto result = file::read(stream, buffer, size * nmemb);
+  return result / size;
 }
 
 } // namespace __llvm_libc